1. Field
This application relates to using accelerometer-based orientation and/or movement sensing to control wearable devices, such as wrist-worn audio recorders and wristwatches.
2. Prior Art
Wrist-worn audio recorders can serve a wide range of uses, from recording memos and meetings for professionals to documenting dietary intake and physical activity for health-conscious individuals and chronicling a child's first words and actions for parents. Furthermore, recorded audio messages can be played back at preset times to remind or alert a user, as disclosed in U.S. Pat. No. 5,511,046 to Vanderpal (1996).
These wrist-worn audio recorders, wristwatches, and related devices are generally controlled through one or more of the following means: electromechanical switches, voice activation, and motion activation.
Switches are commonly used to control functions such as audio recording and playback on devices like electronic wristwatches (as described in U.S. Pat. No. 4,717,261 to Kita et al. (1988)) and, more recently, wrist-worn watch/MP3 players (for example, the Xonix MP3 recorder watches manufactured by Xonix Electronic Watch Co., Ltd., Zhuhai, China). They are also used to report the time in talking watches. However, these switches are often small, difficult to operate, and not very reliable, which may lead to premature failure of the audio recorder or talking watch. In addition, using switches can be inconvenient for recording many brief personal messages, because the user has to remember to turn the audio recorder on and off in order to record each message.
Voice-activated recording mechanisms offer more convenience since they facilitate convenient recording of personal messages only when the user wants to record, without relying on the user's active attention to physically turn the audio reorder on and off during a recording session. However, irrelevant audio signals in the surrounding can still turn on a voice-activated mechanism.
Finally, motion activation has also been used to operate wristwatches. U.S. Pat. No. 3,939,640 to Kahn (1976) describes using a motion-activated switch inside a wristwatch to turn on or off the illumination of a wristwatch display. A free-rolling heavy ball within the container of the switch strikes a spring to cause conduction of electrical current when the wrist rotates rapidly. Additionally, U.S. Pat. No. 4,115,995 to Brien (1978) discloses using a motion-activated switch secured within a wristwatch to set the display on the wristwatch (i.e. to a desired time and date), where quick snaps of the wrist dislodge a metal ball from a magnet and cause conduction of electrical current through the ball. Although these motion-activated switches can be used to turn on and off a wrist-worn device, such as an audio recorder, the rapid motion required to close the electrical switches is unnatural and can cause muscle strain, especially after many repeated actions. Furthermore, it is difficult to add more control functions to a wrist-worn device using only these simple motion-activated on-off switches.
The aforementioned mechanisms for controlling wrist-worn devices leave much to be desired in terms of ease of use and durability. Accelerometer-based methods would offer advantages in these senses, since control can be automatically activated through a user's natural movements, and the user does not need to directly interact with the electromechanical parts of the accelerometer.
In recent years, accelerometers produced with low-cost MEMS (micro-electro-mechanical systems) technology have been used for movement and orientation sensing. For example, the wristwatch described in U.S. Pat. No. 6,513,532 B2 to Mault et al. (2003) uses an accelerometer and a button-controlled audio recorder to monitor physical activity and record dietary consumption, respectively, and U.S. Pat. No. 6,956,564 B1 to Williams (2005) discloses a portable hand-held computer that incorporates two single-axis accelerometers for display control and gesture recognition with small fingertip switches for recording speech notes. In the field of animal behavior monitoring, U.S. Pat. No. 7,246,033 B1 to Kudo (2007) and U.S. Pat. No. 6,263,836 B1 to Hollis (2001) describe the use of accelerometers to monitor pet activity and train dogs, respectively, and both incorporate an audio recorder for recording and playback of a human's voice. However, all of the above accelerometer applications require conventional switches to operate audio recording, so that there still exists a need for the application of accelerometer technology to control recording, playback, time reporting, and other functionality in wrist-worn devices.